Best Foam Filler Material?

Junior Mastermind

I've recently ween working on a new project involving a covering technique of lining it with strips of delaminated foam. This, of course, is not perfect and I'd like to know what would be the best solution to filling the cracks for future sanding and finishing. Any advice?

Old and Bold RC PILOT

It seems you have been reading my project "TODO" list!! Anyway I had struck a similar issue when doing circular planked profile in Paperless FB. I had settled upon then strips of the dreaded Balsa inserted into the gaps and glued in place. I was planning on using 1/32 or 1mm Balsa cut to size of course.

On my trials it sanded quite well and took most finishes very well. A secondary bonus was that the rigidity of the structure was enhanced for very little weight and when dealing with complex curves the Balsa could be shaped using hot water to match the curves before fitting.

Another method I have tried was the use of Foam wedges between the square cut planked pieces and then obtaining the curve with the use of sandpaper. I would sand the Angle required in the uncut foam and then cut it off of the sheet when the angle was right. Tehn apply a little glue and press the wedge into the gap between planks. When the glue was dry I would use a sharp blade and trim the excess off ready for sanding.

Old and Bold RC PILOT

Just another thought if you use a rigid filler you will need to ensure that there is absolutely NO flex in the build because a lot of fillers do dry out and if the build flexes they can fracture of even crumble when flexed repeatedly thereby destroying your perfect finish.

Builder Extraordinare

DAP has changed their formula for their lightweight spackle and this 3M product is my current go-to. Dries fast, sands easy, and you can harden it up with WBPU or epoxy. It will make any dings or hangar rash go away and you can have a perfect surface for whatever you want.

Active member

I've been using white HobbyLite filler lately. It's about 70% more expensive than lightweight spackle, but my spackle started to dry out and turned really gritty and impossible to work with while the HobbyLite filler has stayed really creamy and easy to work with. If it dries out a little, just spritz some water in and stir it back into a paste.

Winter is coming

HobbyLite Filler sounds like Beacon Foam Finisher. I saw it on the shelf of a local hobby store and wanted to check it out, even though it costs about double what the lightweight spackle or the 3M patch and primer. I like foamtac, so figured I'd give it a shot. I like it, and like that it doesn't dry out.